Phosphorylation modulates the activity of the ATP-sensitive K+ channel in the ventromedial hypothalamic nucleus.
Regulation of the ATP-sensitive K+ (K-ATP) channel was examined in cell-attached and inside-out membrane patches of freshly isolated neurons from the ventromedial hypothalamic nucleus (VMN) of 7-14 day old male Sprague-Dawley rats. When inside-out patches were exposed to symmetrical K+, the reversal potential was -2.85 +/- 1.65 mV, the single channel conductance 46 pS, and the total conductance varied as a multiple of this value. Glucose (10 mM) reversibly inhibited channel activity in cell-attached preparations by 81%. In the presence of 0.1 mM ADP, 10, 5, and 1 mM ATP reversibly inhibited VMN K-ATP channels in inside-out patches by 88, 83, and 60%, respectively. This inhibition was not dependent on phosphorylation since 5 mM AMPPNP, the non-hydrolyzable analog of ATP, reversibly inhibited channel activity by 67%. Relatively high concentrations of glibenclamide (100 microM) also reversibly inhibited VMN K-ATP channel activity in cell attached and inside-out patches by 67 and 79%, respectively. Finally, the non-specific kinase inhibitor H7 (200 microM) decreased channel activity by 53% while the non-specific phosphatase inhibitor microcystin (250 nM) increased channel activity by 218%. These data suggest that while the inhibitory effect of ATP is not phosphorylation dependent, phosphorylation state is an important regulator of the VMN K-ATP channel.
Routh
V H
VH
Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Newark 07104, USA. routhvh@umdnj.edu
McArdle
J J
JJ
Levin
B E
BE
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D007033:Hypothalamus, Middle / Q000378:metabolism*; D008297:Male; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013453:Sulfonylurea Compounds / Q000494:pharmacology
D015221:Potassium Channels; D013453:Sulfonylurea Compounds; D000255:Adenosine Triphosphate